In addition to being deadly and devastating, tsunamis tend to arrive without much warning. They’re most commonly triggered by undersea earthquakes and landslides. Those are hard to detect, but getting easier thanks to NEPTUNE, an underwater technology network off Canada’s West Coast.
People need tsunami information fast. On the afternoon of March 11, 2011, an 8.95- magnitude earthquake hit off the coast of Japan. Within an hour, 10-metre waves washed the coast, sweeping away cars, crushing buildings and buckling roads as if they were twist-ties. The 2004 tsunami that swept the Indian Ocean, triggering more tsunamis as it rolled along, was just as shocking; it killed more than 230,000 people in 14 countries, and caused the entire planet to vibrate by about a centimetre.
“The problem is, how do you tell people they’re coming, and more importantly, how do you tell what height they’re going to be?” says Benoit Pirenne, Associate Director, Digital Infrastructure at Ocean Networks Canada.
Enter NEPTUNE, or the North-East Pacific Time-series Undersea Networked Experiments.
Headquartered at British Columbia’s University of Victoria, Ocean Networks Canada is using that high-tech underwater, computer-connected system, and others, to map and monitor the seabed — and to improve detection, warning and analysis of the shapes of the giant waves.
NEPTUNE’s backbone is an 800-kilometre loop of power and fibre-optic cables, connected to equipment that measures a host of geological and other processes, deep in the Juan de Fuca Strait off the B.C. coast. The cable network lies atop the smallest of the Earth’s 12 tectonic plates.
The cables are connected to pressure sensors on the seabed, Pirenne explains. “They’re really scales that measure the water column. They do that every second, so you can map, if you will, every wave,” he says.
Up to now, tsunami detection has been spotty. But NEPTUNE promises to deliver a continuous stream of data that is much more detailed and nuanced than what has been traditionally gleaned from ship-based exploration — and that information, Pirenne hopes, will soon be used to revolutionize tsunami detection.
“We have proven that our sensors can detect their waves,” he notes. “We are now working on the software detection systems and on the models that will help predict more precisely the impacts on specific points along the coast of Vancouver Island.” That step would mean far better protection than the minimal warnings that people have received for tsunamis up to now.
The sensor data is transmitted to stations where scientists can analyze the seismic activity to help predict big waves. “Help” is still the operative word. “In a given time range, with three or more sensors, we can identify the source, origin and the speed of a wave coming toward the coast. But it still doesn’t tell you how high the wave will be,”
Pirenne says.
Tsunamis can reach as high as 30 metres − three times the height of the initial waves that caused the first devastation in Japan. Determining wave height is the next puzzle to solve, says Pirenne.
“We’re working on a detection system. Waves are influenced by the profile of the seabed as you come close to the coastline; the topography of the water [and the seabed underneath] has a big influence on the final speeds and height.
“It’s important take into account the profile of the coastline to see what the wave is going to be doing − whether it’s going to be a metre or 10 metres, an acre or a square kilometre,” he says.
“We hope to have this part ready by the end of 2016.”
The challenge for scientists now is to move tsunami detection forward from its current state of “near-real-time,” with a few minutes lag, to actual real time, so that when waves are detected everyone can know precisely how much time there is to take emergency action. Another challenge is to provide detection for both “near-field”, imminent tsunamis and “far-field” ones that may be on the way.
The scientists are busy and the work is ongoing, says Virginia Keast, Ocean Networks Canada’s communications officer. Last spring, the organization hosted an international workshop to share the latest advancements in tsunami modeling. And in mid-September, Pirenne was in St. John’s, Newfoundland presenting the network’s progress to other experts.
“We’re sharing what we know with Japan, with South America, with other countries,” says Keast. The 2004 Indian Ocean tsunami was the catalyst for action, she says, and this was reinforced by the Japanese disaster in 2011, which sent detritus and debris across the ocean all the way to B.C.
“Canada has one of the most advanced systems in the world in terms of cable sensors supplying data offshore,” says Pirenne.
Graphic: Lauren Heintzman
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